The present invention relates to a hand free device which can be commonly shared by a plurality of communication devices, and more particularly to a hand free device which can be used by a plurality of communication devices simultaneously. Such a hand free device includes a microprocessor, more than one I/O interfaces, a multiplexer control unit, more than one multiplexers, a voice processing unit, a speaker amplifying and control unit, a microphone amplifying circuit, a dialing unit, a charging and power supply unit and an artificial interface. Such a hand free device can be simultaneously coupled to multiple communication devices and allows the same to be operable at the same time.
As a result of fast advancement in communication technology, and the massive investment of private enterprises in this field, cellular phones become so popular that many people are equipped with more than one cellular phones or phone numbers. A conventional hand free device is only applicable to one cellular phone or communication device. If a person is equipped with more than one communication devices, only one communication device is coupled to the conventional hand free device and the rest communication devices are left uncoupled to the hand free device.